<template>
  <div class="spec-preview" @mousemove="handlerMove">
    <img :src="img.imgUrl" />
    <div class="event"></div>
    <div class="big">
      <img :src="img.imgUrl" :style="{ left: bigLeft, top: bigTop }" />
    </div>
    <div class="mask" :style="{ left: maskLeft, top: maskTop }"></div>
  </div>
</template>

<script>
import { throttle } from "lodash";

export default {
  name: "Zoom",
  props: {
    img: {
      type: Object,
      // 给默认值 不然会数据是undefined
      default: () => ({}),
      // required: true,
    },
  },
  data() {
    return {
      // 定义mask位移距离
      maskTop: "0px",
      maskLeft: "0px",
      bigTop: "0px",
      bigLeft: "0px",
    };
  },
  methods: {
    handlerMove: throttle(function(e) {
      let left = e.offsetX - 100;
      let top = e.offsetY - 100;
      if (left <= 0) left = 0;
      if (left >= 200) left = 200;
      if (top <= 0) top = 0;
      if (top >= 200) top = 200;
      this.maskTop = top + "px";
      this.maskLeft = left + "px";
      this.bigTop = -2 * top + "px";
      this.bigLeft = -2 * left + "px";
    }, 100 / 6),
  },
};
</script>

<style lang="less">
.spec-preview {
  position: relative;
  width: 400px;
  height: 400px;
  border: 1px solid #ccc;

  img {
    width: 100%;
    height: 100%;
  }

  .event {
    width: 100%;
    height: 100%;
    position: absolute;
    top: 0;
    left: 0;
    z-index: 998;
  }

  .mask {
    width: 50%;
    height: 50%;
    background-color: rgba(0, 255, 0, 0.3);
    position: absolute;
    left: 0;
    top: 0;
    display: none;
  }

  .big {
    width: 100%;
    height: 100%;
    position: absolute;
    top: -1px;
    left: 100%;
    border: 1px solid #aaa;
    overflow: hidden;
    z-index: 998;
    display: none;
    background: white;

    img {
      width: 200%;
      max-width: 200%;
      height: 200%;
      position: absolute;
      left: 0;
      top: 0;
    }
  }

  .event:hover ~ .mask,
  .event:hover ~ .big {
    display: block;
  }
}
</style>
